Environmental Encyclopedia

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Environmental Encyclopedia 3

Measurement and sensing

ing it the “Silent Spring of the ’90s"—a reference to the book

by Rachel Carson which in 1962 awakened the nation to

the indiscriminate use of pesticides. However, McKibben’s

lament over the “end of nature” is a personal account of

how human activity has changed not just the industrialized

centers of the world, but his own backyard.

McKibbon’s second book, The Age of Missing Informa-

tion (1993), is a study of the seduction of television. On one

day he videotaped every show on every cable channel avail-

able in his area, more than 1,000 hours of television, and

then watched it all. To contrast that experience, he spent a

day camping in the woods near his Adirondack home. “This

book is about the results of that experiment—about the

information that each day imparted,” he says. Talking about

this book, McKibben says, “Television...is a very private

experience, with an almost constant message of ’you are the

most important, this Bud’s for you.’ And if you are at the

center of the world, it’s hard to live environmentally aware.”

McKibben has also edited Birch Browsings: A John

Burroughs Reader (1992).

John Burroughs

, a nature writer

whose career spanned 60 years beginning in 1865, is credited

with establishing the nature essay as a literary genre. Many

environmentalists are returning to the writings of such early

nature writers as Burroughs,

John Muir

, and

Aldo Leopold

to study their ideas about

land stewardship

[Linda Rehkopf]

ESOURCES

OOKS

McKibben, Bill. Birch Browsings: A John Burroughs Reader. New York:

Penguin Books, 1992.

———. The Age of Missing Information. New York: Plume, 1993.

———. The End of Nature. New York: Random House, 1989.

———. Long Distance: A Year of Living Strenuously. Simon & Schuster,

2000.

———. Maybe One: A Case for Smaller Families. Simon & Schuster, 1998.

———. The Return of the Wolf: Reflections on the Future of Wolves in the

Northeast. Middlebury: University Press of New England, 2000.

———. Wolves in the Northeast. University Press of New England, 2000.

Magill, Frank N., ed. Magill’s Literary Annual. Vol. l. Pasadena: Salem

Press, 1990.

Trosky, Susan M., ed. Contemporary Authors. Vol. 130. Detroit: Gale Re-

search, 1990.

ERIODICALS

Walljasper, Jay. “Checking in with Bill McKibben.” Conscious Choice

(July 1999).

MDC

see

More developed country

887

Measurement and sensing

A fundamental premise of all scientific research is that scien-

tists can make measurements, expressed in precise mathe-

matical terms, of conditions and events. Indeed, some argue

that a field of study can only be called a science to the

extent that the data being collected can be mathematically

measured. These criteria apply to

environmental science

as they do to other physical and biological sciences.

Measurements serve a number of functions in environ-

mental studies. One is to provide baseline information about

certain aspects of the

environment

. A source of concern to

scientists and non-scientists alike is the change that appears

to be taking place in the earth’s

ozone

layer. Mounting

evidence appears to suggest that, as a result of human activi-

ties, the concentration of ozone in the

stratosphere

seems

to be decreasing. That finding is significant because the

ozone layer acts as a shield against potentially harmful

ultra-

violet radiation

from the sun.

But how do scientists know that changes are taking

place in the ozone layer? Such a conclusion can be drawn

only if information exists regarding the “normal” concentra-

tions of ozone in the stratosphere. One purpose of measure-

ments, therefore, is to accumulate a huge volume of informa-

tion regarding the “normal” condition of the environment.

A second purpose of measuring is to determine how

some aspect of the environment may be changing, often as

a result of human activities. Our concern about the ozone

layer, for example, arises out of readings taken by high-

flying aircraft over a period of more than a decade. Those

readings show consistent changes (decreases) from the level

that is regarded as natural or normal. These levels are not

fluctuating, that is, decreasing and regaining normalcy.

Rather, there is a trend toward decreased ozone levels.

Dozens of techniques are available for measuring envi-

ronmental characteristics. Many of these techniques are not

unique to environmental science. For example, the use of

thermometers to record temperatures is vitally important in

many environmental studies. But temperature-taking is not

a specialized procedure used by environmental scientists. The

measurement of

radioactivity

is another example. Geiger

counters are used to determine the level of radiation in

environmental studies just as they are in scientific research,

medical applications, industrial processes and other situa-

tions.

Over the years, a number of techniques have been

developed for measuring specific environmental characteris-

tics. Many of these techniques can be classified according

to their use in the measurement of

air quality

water

quality

An example of the former is the high-volume sampler

(HVS) used in measuring particulates in the

atmosphere

Environmental Encyclopedia 3

Measurement and sensing

An HVS is essentially a modified vacuum cleaner that sucks

air into a hose and forces it through a filter paper. The

difference in the weight of the paper before and after it has

trapped the

particulate

matter is used to determine the

weight of the particulates. Since the total volume of air

passing through the HVS can be easily measured, the systems

provides of measure of particulates in mass per volume.

Techniques for measuring various components of a

gas are also becoming more sophisticated. At one time, for

example, the determination of ozone levels was made simply

by suspending a piece of natural

rubber

of known size and

weight in the air. Since ozone causes rubber to crack, the

speed at which cracking occurred was taken as a measure of

ozone levels in the air.

As with most other gases, ozone is now measured by

chemical means. A sample of gas is passed through some

device, often a “bubbler,” that contains a compound that

will react with the gas being tested. The concentration of

that gas can be measured, then, by determining the amount

of chemical change that takes place in the measuring device.

For example, a reaction with which many high school

students are familiar can be used to determine the level of

sulfur dioxide

in the air. Sulfur dioxide reacts with

lead

dioxide (PbO

) to form a characteristic black precipitate of

lead sulfate.

+ PbO

→ PbSO

If lead dioxide is added to a bubbler through which a

sample of gas is passed, the amount of darkening in the

device (due to the formation of lead sulfate) is a measure of

the concentration of sulfur dioxide in the gas.

Many environmental measurements now make use of

sophisticated chemical techniques. One example is infrared

spectrometry. The term spectrometry refers to the measure-

ment of energy absorbed or emitted by various compounds.

All molecules are held together by electrons that vibrate

with characteristic frequencies. If energy is added to those

molecules, they will absorb frequencies of energy that match

their characteristic frequencies, but no others. Each kind of

molecule can be identified, therefore, by a “map” of the

frequencies that it does and does not absorb.

Infrared spectrometry is the most common form of

the technique used because most molecules vibrate with

frequencies in the infrared region. Techniques such as infra-

red spectrometry are valuable because they can detect con-

centrations of a material at much lower levels than can most

chemical systems.

The increasing sophistication of measuring techniques

does not mean that all simple procedures have been aban-

doned. For example, one method for measuring the level of

air pollution

requires no more than good eyesight and a

888

reference card. The reference card contains the Ringelmann

scale, a set of six squares that range from pure white to pure

black. Each square contains an amount of hatching that

corresponds to completely pure air (pure white, no hatching)

to badly polluted air (totally black). The four intermediary

squares contain increasingly more hatching, constituting

equivalents of 20 percent, 40 percent, 60 percent and 80

percent “blackness.”

For comparison, opacity (darkening) of air can also be

determined by electronic means more precisely. A photome-

ter, for example, is a device that records the amount of light

transmitted by a sample of air. The light is converted to an

electric current that can be read on a meter. In some indus-

trial and

power plants

, a photometer is attached to the

smokestack to obtain a continuous record of the opacity of

the gases being emitted.

The two most common types of air quality measure-

ments are those for

ambient air

quality and emissions.

Ambient air refers to the outdoor air that surrounds us.

Ambient air quality measurements provide information on

the possible accumulation of harmful compounds such as

carbon monoxide

, sulfur dioxide,

nitrogen oxides

, and

hydrocarbons

Emission

measurements reveal the level of such com-

pounds being released from a power plant, a factory, or some

other source. In many cases, emissions can be studied by

simply drilling a hole in a smokestack, extracting a small

sample of exhaust gases, and studying their composition by

methods described above.

Many biological, chemical, and physical methods are

available for measuring water quality. The presence of patho-

gens in a sample of water can be determined, for example,

by standard bacteriological techniques in which a water sam-

ple is allowed to incubate for some period of time and the

number of bacteria produced counted visually or electroni-

cally.

At one time, most water tests were fairly straight-

forward chemical tests. The concentration of

nitrogen

in a

water sample, for example, can be determined by a standard

procedure known as the Kjeldahl test and the amount of

chlorination

by precipitation with a silver salt. Today, most

water tests can be conducted by more sophisticated instru-

mental techniques. A photometer can be used to compare

an unknown water sample with a known standard to deter-

mine the concentration of nitrogen,

phosphorus

chlorine

or some other component.

One of the most basic measurements of water quality

is that of oxygen demand. The more polluted a water sample

is, the more organic matter it is likely to contain. The more

organic matter, the greater the amount of oxygen the sample

will require to decompose the organic material.

Environmental Encyclopedia 3

Medical waste

Traditionally, the method for determining this charac-

teristic was

biochemical oxygen demand

(BOD), a test

in which a sample of water is studied over a five-day period.

To overcome the lengthy time required to conduct this test,

modifications such as total organic

carbon

(TOC) have

been developed.

Specialized measuring techniques are sometimes re-

quired for particular types of environmental studies. De-

termining the amount of

noise pollution

in an area, for

example, requires the use of a sound level meter, a device

consisting of a microphone, amplifier, frequency-measuring

circuit, and read-out screen.

One consequence of the improved technology now

available for making measurements is that smaller and

smaller concentrations of a substance can be detected.

Chemical means can routinely detect the presence of a sub-

stance to the level of one part in a thousand or one part per

million (ppm). The most advanced technologies today have

stretched that sensitivity to levels of one part per billion

(ppb) and even one part per trillion (ppt).

The efficiency of these measuring devices poses some

new issues for environmentalists. What does it mean, for

example, to learn that a

toxic substance

exists in the

soil

at a level of one ppb if we know the material is harmful only

in much higher concentrations? Does any level of exposure to

the substance pose a hazard, or can we safely ignore such a

minuscule quantity of the substance?

A field of measurement of increasing importance in

environmental studies is remote sensing. The term refers to

any method by which an object or an area is studied at some

great distance. Most commonly today, the term is used to

describe surveys of the earth’s surface by satellites orbiting

around it.

Remote sensing procedures depend on the fact that

various types of materials absorb and reflect

solar energy

in different ways. Instruments in satellites that can measure

these differences can, therefore, detect variations in land and

ocean surfaces.

Remote sensing uses three parts of the electromagnetic

spectrum: the visible, infrared, and microwave regions. Per-

haps the most common form of remote sensing is that which

uses photography. Photographic equipment has now been

developed to the point where objects of no more than a few

yards apart can be distinguished from outer space.

Since some objects and features emit radiation in elec-

tromagnetic regions other than the visual, infrared, and mi-

crowave techniques are also used. The images obtained from

any one of these methods can be further improved by com-

puter enhancement of the original photographs.

Remote sensing has now been used for a number of

environmental applications. Some examples include the lo-

889

cating of possible mineral reserves, the tracing of water

drainage

patterns, the determination of soil moisture, the

tracing of plant diseases, the calculation of snow and ice

masses, and the measurement of biological productivity in

the oceans. See also Drinking-water supply; Emission stan-

dards; Greenhouse gases; National Ambient Air Quality

Standards; Ozone layer depletion; Radiocarbon dating;

Water pollution

[David E. Newton]

ESOURCES

OOKS

McGraw-Hill Encyclopedia of Science & Technology. 7th ed. New York:

McGraw-Hill, 1992.

Vesilind, P. A., J. J. Peirce, and R. Weiner. Environmental Engineering.

2nd ed. Boston: Butterworths, 1988.

Medical waste

Medical waste is a subcategory of

hazardous waste

that

is attracting increasing concern. The

Environmental Pro-

tection Agency

(EPA) lists the following categories of med-

ical waste: cultures and stocks; pathological wastes which

includes body parts; blood and blood products; used “sharps”

such as needles and scalpels;

animal waste

or animal corpses

which have been inoculated with infectious substances in

medical research; isolation wastes, which come from people

with highly contagious diseases; and unused, discarded

“sharps.”

Ten to fifteen percent of medical waste is considered

infectious, although guidelines on just what is infectious

medical waste vary from state to state. As a result, state

and federal guidelines on disposal of these wastes are a

hodgepodge of confusing laws and regulations. And the

guidelines that do exist usually exempt generators of 50

pounds (23 kg) or less per month from any regulatory action.

The need to address medical waste began soon after

such items as syringes, IV bags, and scalpels were observed

washing up on ocean beaches in the summer of 1988. Con-

gress directed the EPA to gather data on their sources,

associated health hazards, and current procedures and regu-

lations for management and disposal and to evaluate the

health hazards associated with transporting them, incinerat-

ing them, burying them in a

landfill

, and disposing of them

in a sanitary sewer system.

A two-year, voluntary program enacted by Congress,

the Medical Waste Tracking Act of 1988, was instituted in

response to public concern over the treatment of medical

waste. The Act created a “cradle-to-grave” tracking system

based on detailed shipping records, similar to the program

in place for hazardous waste. The pilot program has now

Environmental Encyclopedia 3

Medical waste

expired, the EPA data has been sent to Washington adminis-

trators, and any action on the findings of the EPA’s study

is in limbo. It is doubtful that the EPA report on medical

waste will ever be submitted to Congress or find its way

into the Federal Register because many of the states that

participated in the program went on to pass strict medical-

waste management guidelines of their own. All the states

participating at least revised their

municipal solid waste

guidelines to include the category of medical waste, whether

or not management practices were included.

Another complicating factor in the regulation of medi-

cal waste is that at least four different federal agencies are

involved with medical-waste issues: the EPA, the

Occupa-

tional Safety and Health Administration

(OSHA), the

Centers for Disease Control (CDC), and the

Agency for

Toxic Substances and Disease Registry

The EPA’s study reported that 3.2 million tons of

medical waste was produced in the United States each year.

Not surprisingly, hospitals, long-term health care facilities,

and physician’s offices are the major producers of medical

wastes, which account for about 0.3% by weight of all munic-

ipal

solid waste

. The EPA found out that current practices

of management and disposal range from handling the waste

as nonhazardous municipal solid waste to strict segregation,

packaging, labeling, and tracking from the generator to the

disposal site, the so-called “cradle-to-grave” management.

Health care workers are required by federal law to

segregate medical waste in special containers; if the waste

is transported for treatment, it must be labeled with the

generator’s name and carry a biological hazard symbol. But

facilities that produce less than 50 lb (23 kg) of medical

waste per month are exempt from most requirements. Home

and small generator medical wastes fall through the cracks.

Insulin-dependent diabetics, for instance, typically dispose

of used syringes in their household trash or flush them down

the toilet. In some northeastern cities, New York City for

example, antiquated sewage systems pour material into rivers

and oceans during heavy rainfalls. Depending on tides and

currents, syringes can end up on beaches, which is what

New York and New Jersey coastlines experienced in 1988

and 1989.

A growing source of medical waste that is not regulated

is that generated by home health-care providers. As a result

of new patient-care strategies and rising medical costs, more

long-term illnesses are being treated at home. That means

that medical waste is being disposed of in ordinary household

trash. Medical clinics and intravenous drug users are also

suspected of contributing to unsafe dumping of medical

wastes. Even U.S. Navy vessels contributed to beach medical

waste.

The need to address the problem evolved long before

wastes washed up on northeastern beaches, however. Over

890

the last 10 years, and partly in response to the

AIDS

and

hepatitis epidemics, the use of disposable health care prod-

ucts has contributed to the increased volume of medical

waste. Cost-containment measures have increased the use

of plastic disposables in health care settings. From syringes

to bedpans, health care aids are increasingly thrown away.

Common treatment techniques of medical waste in-

clude steam sterilization and

incineration

, although some

waste is discarded into sewage systems. During autoclaving,

the waste is exposed to steam at a temperature of 250°F

(121°C) for at least 45 minutes. Autoclaving fails to reduce

the volume of waste that must be landfilled, and is only

preferred in areas where there is no appropriate incineration

equipment. Proper incineration efficiently destroys all cate-

gories of infectious wastes, effectively kills live and dormant

forms of pathogenic organisms, and alters the waste volume.

About 60 percent of medical waste is treated on site

at hospital facilities. After treatment, ash residues or steri-

lized and disinfected materials must be transported to com-

mercial treatment facilities or taken directly to landfills.

Other options for medical waste treatment include

compac-

tion

, microwaving, and mechanical or chemical disinfection,

which could be less costly and alleviate concerns about emis-

sions from incinerators.

According to the congressional Office of Technology

Assessment (OTA), air emissions of

dioxin

and

heavy

metals

from hospital incinerators average 10 to 100 times

more per gram of waste burned than emissions from well-

controlled municipal waste incinerators. And while waste

generators are generally required to track with manifests the

route their wastes take to reach disposal, strict requirements

do not exist for on-site treatment facilities.

Some industry watchers, environmentalists, and policy

makers are advocating a medical waste disposal program

similar to some in Europe. Virtually all medical wastes in

Switzerland and Germany, for example, go to regional incin-

eration facilities. Stringent air-quality regulations in these

countries make it impractical for hospitals to do on-site

incineration, but the regional facilities made advanced

air

pollution control

devices cost-effective. In Munich, opera-

tors dump the resulting ash in specially lined landfills. Hospi-

tals in Canada are turning away from disposable supplies in

favor of products that can be cleaned and reused.

For a regional system to work, however, medical waste

must be safely transported. In the United States, there are

no federal statutes governing the transport of medical refuse.

Refrigerated trucks legally can and do carry food after trans-

porting medical wastes.

A proposal to manage home users of syringes and

medicines that end up in municipal solid waste landfills

would include a pharmacy “swap” system. In Switzerland

and Germany, for example, pharmacies accept old medicines

Environmental Encyclopedia 3

Mediterranean fruit fly

for appropriate disposal, then send the medicine to regional

incineration outlets. A deposit-and-return system on syrin-

ges has been advocated in this country to insure the safe

disposal of syringes.

[Linda Rehkopf]

ESOURCES

OOKS

Moeller, D. W. Environmental Health. Cambridge: Harvard University

Press, 1992.

ERIODICALS

Carlile, J. “Finding Disposal Options for Medical Waste.” American City

and County (November 1989): 66.

Groves, L. “Hospitals Re-Think Disposables.” Alternatives (January-Febru-

ary 1993): 13.

Hershkowitz, A. “Without a Trace: Handling Medical Waste Safely.”

Technology Review (August-September 1990): 35.

“Managing Medical Waste.” The Futurist (September-October 1991): 49.

“Tracking Seaside Medical Wastes.” Science News (September 16, 1989):

191.

Mediterranean fruit fly

The Mediterranean fruit fly (referred to as Med fly, or Mos-

camed in Spanish), Ceratitis capitata, is one of the most

destructive fruit pests in the world. The United State has

suffered infestations of Med fly in California, Texas, and

Florida, but with aggressive detection and eradication pro-

grams, the Med fly has not yet become established in the

United States. However, eradication efforts are difficult and

expensive. There is a loss of crop yield associated with the

infestation, control measures are costly, and both fresh and

processed fruit and vegetables must be sorted. Some coun-

tries maintain quarantines against the Med fly, which elimi-

nates potential markets when Med fly becomes established

in an area.

The Med fly, which originated in Africa, is widely

distributed throughout the world, as it has a wide range of

hosts and is able to tolerate colder climates better than most

other

species

of fruit flies. It has caused infestations in over

85 countries in tropical and subtropical regions. Since 1929,

the United States has been involved in several outbreak and

eradication programs. The Med fly became established in

Hawaii in 1910. Hawaii remains infested, and there is no

eradication program currently under way.

Med fly larvae can develop and feed on most decidu-

ous, subtropical, and tropical fruits and some vegetables. It

has been shown to attack more than 260 different fruits,

flowers, vegetables, and nuts. The Med fly prefers thin-

skinned, ripe succulent fruits such as deciduous fruits (for

example, pear, peach, and apple) more than citrus fruits.

891

The larvae feed on the pulp of fruits, tunneling through it,

and reducing the fruit to an inedible juicy mass. In the

Mediterranean countries, often only the earlier maturing

fruits are grown, because later maturing fruits would be

too heavily infested to be marketable. Harvesting before

complete maturity is also practiced in Mediterranean areas

with Med fly infestations.

The adult Med fly is slightly smaller than a common

housefly. It is colorful, with dark blue eyes, shiny black

thorax (back), and a yellowish abdomen with silvery cross

bands. Its droopy wings are covered with yellow, brown, and

black blotchy spots and bands.

The life cycle of the Med fly has fives phases: (1) the

adult female pierces the skin of a fruit or vegetable with a

needle-like ovipositor and deposits one to 10 eggs (other

Med flies may deposit in the same puncture); (2) eggs hatch

into maggots (worm-like, legless larvae); (3) larvae feed upon

the pulp of the fruit or vegetable before dropping to the

ground; (4) the larvae transform into pupae into the

soil

;

and (5) the pupae mature into adults and emerge from the

soil. The life cycle is completed in 21–30 days under tropical

summer weather conditions.

An eradication program consists of three areas of ac-

tion: survey, regulation, and control.

The Animal and Plant Health Inspection Service

(APHIS) of the

U.S. Department of Agriculture

in cooper-

ation with state departments of agriculture survey high-

risk areas of states susceptible to Med fly infestations by

conducting

trapping

programs. If one or more Med flies

is collected in a trap, APHIS and state officials implement

a survey to determine if there is an infestation and if so, to

define the limits of the infested area. Using the original

detection site as the focal point, additional traps are placed

and monitored.

If an infestation is identified, then federal and state

regulations dictate that a quarantine must be imposed to

prevent the spread of the Med fly. Federal quarantine laws

prevent the interstate movement of any article that might

harbor the fly. State regulations control the movement of

these articles going to uninfested areas within the same state.

The regulated articles include all of the fruits and vegetables

within the area that could serve as a Med fly host. Open-

air vegetable and fruit stands are required to cover produce

to prevent infestation. All commercial and home-grown pro-

duce may not be transported without inspection and

treatment.

To eradicate a Med fly infestation, three kinds of

treatment are used alone or in combination. An aerial and

ground bait spray can be used that contains a protein/sugar

bait to attract the fly and an insecticide in minimal amounts

to kill the flies.

Environmental Encyclopedia 3

Mediterranean Sea

In the Sterile Insect Technique (SIT), Med flies are

raised in large numbers, sterilized with a non-lethal dose of

irradiation, and released into infested areas, where they mate

with the wild Med flies. As these matings do not produce

offspring, the wild population is eliminated through attri-

tion. This technique is most effective in areas with low Med

fly populations where a high proportion of sterile to wild

Med flies can be achieved. Before the use of SIT, bait spray

can be applied to decrease local populations down to lower

densities.

The third method is to apply insecticide to the soil

under host trees, where the insecticide kills some larvae as

the enter the soil to pupate but most of the adults as they

emerge from the ground. Application of insecticide to the

soil is used only when larvae are detected. The preferred

method of eradication control is an integrated approach,

using all three treatments, with the use of SIT emphasized.

To prevent Med flies from being brought into the

United States, APHIS administers agricultural quarantine

laws to keep foreign plant pests and diseases from being

brought into the country. Travelers coming to the continen-

tal United States from Hawaii or a foreign country are not

allowed to bring into the country fresh fruits, meats, plants,

birds, and plant and animal products. In fiscal year 1998,

when 400,000 aircraft were cleared to bring travelers and

cargo into the United States, APHIS officers intercepted

more than 1.8 million illegal plants, animals, or plant and

animal byproducts. More than 52,000 plant pests and dis-

eases known to be dangerous to the U.S. agricultural industry

were also intercepted.

If Med fly were to become established in the United

States, prices of fruits and vegetables would increase, and

produce would become less available. Both commercial pro-

duction areas and backyard gardens would require the appli-

cation of more pesticides on a regular basis. In 1993, APHIS

estimated that annual losses due to Med fly infestations

would be about $1.5 billion annually, if Med fly were to

become established in the United States. These losses would

be due to export sanctions, lost markets, treatment costs,

reduced crop yields, and premature fruit drop.

[Judith L. Sims]

Mediterranean Sea

For centuries, the Mediterranean Sea has been the focal

point of western civilization. It is an area rich in history and

has played critical roles in the development of shipping and

trade, as a resource for feeding growing populations, and as

an aid to the spread and mingling of races and cultures.

The Mediterranean began to form about 250 million

years ago when the Eurasian and African continental plates

892

began moving toward each other, pinching off the Tethys

Sea, an extensive shallow sea that separated Europe and

much of Asia from Africa and India. It now has only two

outlets, the Straits of Gibraltar and the Bosporus, a narrow

strait between the Mediterranean and Black Seas. While the

central basin of the Mediterranean reaches depths of several

thousand yards, there is a sill under the Straits of Gibraltar

that is only 1,970 feet (600 m) below the surface. Through

this passageway flows surface water from the Atlantic Ocean.

Since the Mediterranean is situated in one of the

world’s

arid

belts, the inputs from precipitation and rivers

is far less than the water lost through evaporation. If the

straight at Gibraltar were to close due to further plate move-

ments, the Mediterranean would dry up. In fact, data from

the Deep Sea Drilling Project, seismic surveys, and fossil

analysis have found evidence of salt deposits, ancient river

valleys, and fresh water animals, all suggesting that this has

occurred at least once. Since the African and Eurasian plates

are moving together, this will probably happen again.

Humans can do nothing about this impending geolog-

ical disaster. There are, however, events that people can

influence. Domestic sewage, industrial

discharge

, agricul-

tural

runoff

, and

oil spills

are seriously threatening the

Mediterranean, fouling its once clear waters, altering its

chemical cycling, and killing its organisms. Along its north-

ern coastline are some of the most heavily industrialized

nations in the world, whose industries are destroying near-

shore nursery habitats, damaging fisheries.

Dams

on in-

flowing rivers reduce the

sediment

inputs, making coastal

erosion

a major problem. Shipping, once the hallmark of

Mediterranean civilization, releases every manner of waste

into the Sea, including oil. Annually, 6 million barrels of oil

end up in the Mediterranean. The limited water circulation

patterns of the Mediterranean compound this problem as

pollutants accumulate.

Today seafood contamination and eye, skin, and intes-

tinal diseases are frequently experienced by coastal residents.

Marine mammal and sea turtle populations are threatened

habitat

loss and nondegradable pollutants dumped into

the waters. Sea grass (Posidonia oceanica), which provides

food and habitat for some 400

species

of algae and thou-

sands of species of fish and invertebrates, is disappearing.

Nutrient

enrichment of the Mediterranean results in large

plankton

blooms which, combined with destructive fishing

practices, contribute to the demise of the sea grass beds.

These problems have been recognized, and efforts are

being made to reverse the declining health of the Mediterra-

nean. Early efforts included the 1910 construction of one

of the first institutions for study of the seas, the Muse

Oceanographique by Prince Albert I of Monaco. Since then,

the conflicts between the political and religious ideologies

of the 18 nations surrounding the Mediterranean have been

Environmental Encyclopedia 3

Chico Mendes

major hurdles in completing cleanup plans. In 1976, the

Mediterranean Action Plan was signed by 13 of the nations.

A major component of this agreement was the Blue Plan,

a study of future effects of increasing coastal populations.

Other efforts include the Genoa Declaration in 1985 and

the Nicosia Charter in 1990. The latter commits resources of

the community, the

World Bank

, the European Investment

Bank, and the

United Nations Environment Programme

to achieve a Mediterranean

environment

compatible with

sustainable development

by 2025. Hopefully, these efforts

can reverse the decline of this natural wonder. See also Algal

bloom; Biofouling; Commercial fishing; Environmental

degradation; Ocean dumping; Water pollution

[William G. Ambrose and Paul E. Renaud]

ESOURCES

OOKS

Heezen, B. C., and C. D. Hollister. Faces of the Deep. London: Oxford

University Press, 1971.

Thurman, H. V. Essentials of Oceanography. Columbus: Merrill, 1983.

ERIODICALS

Batisse, M. “Probing the Future of the Mediterranean Basin.” Environment

32 (1990): 4–15.

Megawatt (MW)

A megawatt is a unit of power equivalent to one million

watts (10

watts), or one thousand kilowatts. As a unit of

power, a megawatt expresses the rate at which energy is

produced. A megawatt is equivalent to one million joules

per second. A megawatt is a fairly large unit of power and

is used, therefore, when discussing the size of a power plant,

a nation’s total energy-generating capacity, or some other

such large statistic. For example, the total electrical energy

generating capacity for the state of California in 1988 was

45,900 megawatts. See also Energy and the environment;

Energy efficiency

Chico Mendes (1944 – 1988)

Brazilian union leader, conservationist, and activist

Francisco Alvo Mendes Filho, known as Chico Mendes,

was a defender of the tropical rain forests and a champion

of the concept of sustainable harvest as a means of saving

and protecting that threatened

ecosystem

. As president of

the local Rural Workers Union, representing

rubber

tappers

in his native Brazil, Mendes became too powerful and politi-

cally influential for ranchers who wanted to turn the

rain

forest

into grazing land for their cattle. The struggle be-

tween them ended in 1988, when Mendes was assassinated.

893

Chico Mendes. (Corbis-Bettmann. Reproduced by per-

mission.)

Chico Mendes was born in 1944 in Acre Province of

Brazil, along the upper reaches of the Amazon River not

far from the border with Peru and Bolivia. Following his

father, he was a seringueiro, a rubber tapper. He farmed a

small clearing, but relied on the sale of rubber from several

hundred native rubber trees in the rain forest itself to provide

income for him and his family. Mendes inherited the land

and the trees from his father who had begun tapping them

in the 1930s. Two long v-shaped cuts made with care in

the bark of each rubber tree would yield one or two cups of

the milky latex sap each week, which could then be dried

to make natural rubber.

Mendes would also collect other natural forest prod-

ucts, such as fruits and Brazil nuts, to supplement his income.

There are approximately 100,000 other rubber tappers living

throughout the rain forest, and this is what they do as well.

It is sustainable harvest which does not destroy the forest

and provides a substantial income. On average,

logging

yields a one-time profit of $1,290 per acre; if the land is

converted to cattle pasture, it yields an income of about $61

per acre per year. The sustainable yield of forest products,

on the other hand, provides an income of $2,762 per acre

per year.

Land speculators and large cattle ranching concerns

are more interested in the short-term profits they can realize

Environmental Encyclopedia 3

Mercury

by cutting down the forest, selling the timber, and converting

the land for cattle grazing. Ranching requires huge tracts of

land, and satellite images indicate that in 1988 alone about

30 million acres of forest was destroyed for this industry.

Low land prices, low tax rates, and direct subsidies to

ranchers further encourage this practice. The Brazilian gov-

ernment had further aided ranching by building and main-

taining roads into the forest, which are then used to ship

cattle to market.

Chico Mendes fought to end this destruction of the

tropical rain forest

. He made many political inroads, gain-

ing influence with the Interior Ministry as well as the public.

His main adversary was Darli Alves da Silva, a cattle rancher

who had begun acquiring forest land in Acre through strong-

arm tactics and he vowed that Mendes would not live out

1988. Mendes had helped establish several forest reserves

that year, thus all but ending forest clearing in Acre.

Mendes, his wife, and two policemen assigned to guard

him were playing cards at his home on the night of December

22, 1988. Mendes stepped outside for a moment and was

killed by a shotgun blast to the chest from a waiting assassin.

The local police claimed no clues or suspects in the case,

but local and international protests forced the Brazilian gov-

ernment to enter the investigation. Evidence led them to

the ranch of Darli da Silva. In the summer of 1989 indict-

ments for murder were handed down to Darli da Silva, his

son Darci Pereia da Silva, and Jerdeir Pereia, one of da

Silva’s ranch hands. Testimony indicated that Darli ordered

the murder and that Darci supervised as Jerdeir carried out

the plot. There is evidence that other prominent ranchers

may have been involved in the plot, and they are currently

under investigation.

[Eugene C. Beckham]

ESOURCES

OOKS

Dwyer, A. Into the Amazon: The Struggle for the Rain Forest. San Francisco:

Sierra Club Books, 1990.

Revkin, A. The Burning Season: The Murder of Chico Mendes and the Fight

for the Amazon Rain Forest. New York: Houghton Mifflin, 1991.

ERIODICALS

Willrich, M. “Murder in Acre.” Amicus Journal 11 (Spring 1989): 10–13.

Mercury

Mercury is a naturally occurring element in minerals, rocks,

soil

, water, air, plants, and animals. The predominant forms

in the

atmosphere

, water, and

aerobic

soils and sediments

are elemental and mercuric mercury; while cinnabar is com-

monly found in mineralized ore deposits and

anaerobic

894

soils and sediments. Mercury is present throughout the at-

mosphere because of its relatively high vapor pressure. It

vaporizes from the earth’s surface and is transported in a

global cycle, sometimes for hundreds of kilometers, before

being deposited again with particulates, rain, or snow. The

background concentrations in rocks and soils typically range

between 20 and 100 ␮g Hg/kg with a worldwide average

of about 50 ␮g Hg/kg. Natural background concentrations

in the uncontaminated atmosphere are in the order of be-

tween 1 and 10 ng/m

increasing to between 50 and

1,000,000 ng/m

or more over mineralized areas. Mercury

is transported to aquatic ecosystems via surface

runoff

and

atmospheric deposition

. Airborne concentrations associ-

ated with

anthropogenic

activities such as

coal

burning,

smelting, industry, and

incineration

range between 100 and

100,000 ng/m

The annual worldwide production from cinnabar was

about 11,500 metric tons in 1990. The element can be di-

vided into two major categories, organic and inorganic. Inor-

ganic mercury includes the elemental (Hg

) silvery liquid

metal (mp, 38°C; bp, 357°C) as well as mercurous

ion

(Hg

mercuric ion (Hg

), and their compounds. Organic mercury

includes chemical compounds which contain

carbon

atoms

that are covalently bound to a mercury atom, such as methyl-

mercury (CH

-Hg

During the latter half of the twentieth century, inor-

ganic mercury was used extensively to produce caustic soda

and

chlorine

as well as to manufacture batteries, switches,

street lamps, and fluorescent lamps. Gold mining, dental

amalgams, pharmaceuticals, and other consumer items also

consume inorganic mercury. Organic mercury applications

have mostly been eliminated in agricultural fungicides, slimi-

cides in paper pulp production, bacteriostats in water based

paints, and industrial catalysts.

Over the centuries the symptoms of inorganic mercury

poisoning

were well documented by the exposure of miners

and industrial workers as mercury accumulated in their

brains, kidneys, and livers. Loose teeth, tremors, and psycho-

pathological symptoms were common at low exposure, but

removal from the source would often enable the victims to

recover. However, the effects of organic alkyl mercurials,

such as methylmercury, were more severe. With a

half-life

in the human body of about seventy days, continued exposure

elevates the levels. It also crosses the blood/brain and placen-

tal barriers, attacking the central nervous system and induc-

ing teratogenic changes in the fetus. The neurological symp-

toms include: loss of coordination in walking; slurred speech;

constriction of the field of vision; loss of sensation, especially

in the fingers, toes, and lips; and loss of hearing. Severe

poisoning can cause coma, blindness, and death.

The concentrations of mercury in the ocean and un-

contaminated freshwater are generally believed to be less

Environmental Encyclopedia 3

Metals, as contaminants

than 300 and 200 ng/l respectively. However, new ultra clean

analytical techniques indicate that the actual concentrations

may be three to five fold lower. In contaminated aquatic

systems concentrations as high as 5 ␮g Hg/l have been

reported. In the water column, mercury readily adsorbs onto

organic particulates, metal oxides, and clays. Then they settle

into the sediments. Historically, depending on their location,

the natural background concentrations of mercury in sedi-

ments have ranged between 10 and 200 ␮g/kg. However,

most aquatic systems have received some mercury contami-

nation, and the rate has increased during the past century.

Among sites that have been measured, the total concentra-

tions have usually been from five to ten times greater than

background and ranged from less than 0.5 mg Hg/kg (dry

weight) in remote areas to 2010 mg Hg/kg (dry weight) in

Minamata Bay, Japan.

In the aquatic

ecosystem

inorganic mercury is con-

verted to methylmercury by both biotic and abiotic processes.

It is then released, and aquatic organisms bioaccumulate it

easily and metabolize and excrete it very poorly. The biologi-

cal half-life in fish may be as long as one to three years.

Exposed organisms at each level of the food chain bioconcen-

trate methylmercury and pass it on to animals at the higher

trophic levels.

Depending on the

species

of fish and the type and

amount of mercury being released from the sediments, it

may be magnified biologically from 1,000 and 100,000 times

or more. While background levels of total mercury in fresh-

water and marine fishes from unpolluted waters typically

range from less than 0.1 to about 0.2 mg Hg/kg, higher

concentrations are found in some pelagic top predator ocean

fishes such as tuna and shark, sometimes exceeding 1.5 mg/

kg. Conversely, fish from contaminated waters typically con-

tain levels between 0.5 and 5.0 mg Hg/kg and up to 35 to

50 mg Hg/kg in highly contaminated areas.

Several standards have been developed to protect the

public’s health from the threat of mercury poisoning. The

maximum permissible concentration

allowed by the

United States

Environmental Protection Agency

(EPA)

under its drinking water standards is 2 ␮g Hg/l. The United

States

Food and Drug Administration

guideline for mer-

cury in seafood is 1 mg Hg/kg freshweight; however, some

states, such as Michigan, adhere to a more restrictive guide-

line of 0.5 mg Hg/kg freshweight. The Food and Agriculture

Organization of the United Nations (FAO), on the other

hand, recommends a provisional tolerable intake (PTI) of

0.3 mg mercury per week for a person weighing 154 lb (70

kg), of which no more than 0.2 should be in the methylated

form. See also Biological methylation; Birth defects; Food

chain/web; Minamata disease; Teratogen; Water pollution;

Xenobiotic

[Frank M. D’Itri]

895

ESOURCES

OOKS

D’Itri, F. M., et al. An Assessment of Mercury in the Environment. Washing-

ton, DC: National Academy of Sciences, 1978.

ERIODICALS

D’Itri, F. M. “Mercury Contamination: What We Have Learned Since

Minamata.” Environmental Monitoring and Assessment 19 (1991): 165–82.

Metabolism

The sum total of biochemical reactions occurring in living

organisms by which energy is made available to the organism.

Metabolism consists of catabolism, the chemical breakdown

of large molecules into their smaller molecular components

(e.g., from proteins to amino acids), and anabolism, the re-

construction or chemical synthesis of large molecules. In

physiology, metabolism also describes regulated sequences of

chemical reactions (physiological pathways), such as protein

metabolism or urea metabolism. In

ecology

, the metabolism

of lakes or ponds is the sum of the chemical reactions taking

place between the inhabitants and the

environment

Metals, as contaminants

Metals, objects made from metal, and chemical compounds

containing metal are pervasive in the home, workplace, and

environment

. Although metals play an essential role in

modern human society, there are many instances where they

occur as unneeded and harmful contaminants.

Heavy met-

als

such as

mercury

cadmium

lead

uranium

, chromium,

manganese,

nickel

, thallium, and bismuth are all industrially

useful, but they are also potentially harmful at high concen-

trations in the environment or when found in food or drink-

ing water. Environmental contamination with heavy metals

can result from many activities including mining, large-scale

combustion

coal

in heating or

power plants

, mineral

and metal processing, and use of fungicides and pesticides.

The metal mercury (Hg), a useful component of many

products including thermometers, pesticides, drugs, paints,

and batteries, is unusual in that it is a liquid at ordinary

temperatures. It forms a variety of useful salts and organic

compounds. Misuse of products containing mercury can lead

to serious health problems. Disorders caused by mercury

depend on the form of mercury ingested and the method

of exposure. Ingestion of mercury salts can lead to kidney

damage and death. Exposure to mercury vapor can lead to

inhalation or

absorption

through the skin. Brain function

is affected, and loss of memory, depression, anxiety, and

other personality changes may result. Ingestion of organic

mercury compounds used in pesticides can result in perma-

nent neurological damage. One very serious mercury

pollu-

Environmental Encyclopedia 3

Meteorology

tion

incident occurred in the 1950s at Minamata Bay, Japan,

where releases of mercury in

effluent

from a manufacturing

plant were ingested by fish. People eating the fish developed

serious, and in some cases fatal, neurological maladies. In-

fants and children were particularly vulnerable to this “Mini-

mata disease.”

Lead (Pb) has been used for many purposes for thou-

sands of years. However, toxicity has been largely unnoticed

or ignored until recent decades. Lead uptake by the body is

quite slow, but its rate of excretion is even slower. Thus in

cases of long term exposure, lead levels in the body gradually

increase. There are many sources of contamination. Lead

water pipes were once used to carry domestic water. Until

recently, lead-containing solder was use to join

copper

pip-

ing in homes. Lead contamination of drinking water re-

sulted, and symptoms of lead toxicity were noted in those

who used the water. Until recently, white lead pigment was

widely used in house paint. Deteriorating and chipping paint

poisoned occupants, particularly children, who accidentally

ingested or inhaled dust and fragments. Symptoms of lead

toxicity can be both chronic and acute. Weakness, loss of

appetite,

anemia

, vomiting, and convulsions have all been

reported. Lead causes lesions in the central nervous system

and serious long-term damage.

Cadmium (Cd) is useful both as an element and in

compounds. The element is a lustrous silvery metal that is

usually associated in

nature

with zinc. It is used to plate

steel, copper, brass, and other alloys and serves to retard

corrosion. Cadmium oxide is used in nickel-cadmium stor-

age batteries and as a pigment in paints and inks. Although

metallic cadmium is not dangerous under ordinary condi-

tions, cadmium ions, produced when the metal is attacked

by mineral acids, are very toxic. Toxicity symptoms resemble

those of mercury.

Uranium (U) with an atomic number of 92, is one of

the heaviest of all elements. Once thought to be rare, it is

now known to be widely distributed in the Earth’s crust. Its

concentration in sea water exceeds those of mercury and

cadmium and is at about the same level as copper and lead.

Interest in uranium and its use expanded dramatically with

the development of atomic power and

nuclear weapons

Environmental and health concerns have centered on the

radioactive nature of uranium, but chemical toxicity is also

a potential problem. Uranium contamination surrounding

mining and mill

tailings

in southwestern United States has

been a major concern for Native Americans living nearby.

Each of the heavy metals has its own specific toxic

effects on human health and the environment. Before this

fact was generally realized, mining, smelting and manufac-

turing activities often resulted in appalling instances of envi-

ronmental contamination. While greater concern has re-

896

sulted in improvement, serious problems remain in instances

where proper control has not been practiced.

[Douglas C. Pratt Ph.D.]

ESOURCES

OOKS

Baselt, R. C. Disposition of Toxic Drugs and Chemicals in Man. 3rd ed.

Chicago: Year Book Medical Publishers, 1989.

Eichstaedt, P. H. If You Poison Us: Uranium and Native Americans. Santa

Fe.: Red Crane Books, 1994.

Friberg, L., et al., eds. Handbook on the Toxicology of Metals. 2nd ed.

Amsterdam, New York: Elsevier, 1986.

Meteorology

Meteorology is derived from the Greek words meteora mean-

ing things in the air or things above, and logy meaning

science or discourse. It is a branch of physics concerned

with the study and theory of atmospheric phenomena and

is frequently equated to atmospheric science. One of the

earliest references to this branch of physics is Aristotle’s

Meteorologica written around 340

B.C.

In the modern context meteorology is founded upon

the basic physical principles and laws governing the energy

and mass exchanges within the earth’s

atmosphere

and

involves the study of short term variations of atmospheric

properties (temperature, moisture, wind) and interactions

with the earth’s surface. The ability to predict and explain

short term changes in the atmosphere from observations and

numerical models (using the laws of physics) is an important

dimension of meteorology as well. Thus the words meteorol-

ogist and forecaster are often used interchangeably to de-

scribe someone who can predict the weather.

Meteorologists are trained in observations, instrumen-

tation, data processing, and

modeling

techniques for the

purpose of analyzing and predicting trajectories of major

weather systems, including their associated temperature, pre-

cipitation, wind, and sky conditions. Modern methods in-

clude the use of automated surface observation systems, ra-

dar, satellites, radiosondes, wind profilers, and high

resolution computer models (sometimes called global circu-

lation models) to estimate temporal and spatial variability.

See also Acid rain; Climate; Cloud chemistry; Hydrologic

cycle; Photochemical smog

Methane

An organic compound with the chemical formula CH

methane occurs naturally in air at a concentration of about

0.0002 percent. It is produced in processes such as the

an-

aerobic

decay of organic matter, the growth of certain types